US President Barack Obama has announced a series of fresh sanctions against Russia over its actions in Ukraine - prompting an immediate retaliation from Moscow.

In a speech on the White House lawn, Mr Obama said 20 individuals linked to the Russian government would be targeted for increased sanctions. A bank supporting those individuals will also be hit.

Among the senior Russian figures sanctioned by the US is Sergei Ivanov, one of President Vladimir Putin's closest associates.

Also being hit is Yuri Kovalchuk, who is considered to be Mr Putin's private banker, and two life-long friends who have become multi-billionaires during Mr Putin's presidency.

Moscow immediately banned nine US officials and politicians from entering Russia in retaliation.

A list of banned individuals released by the Russian Foreign Ministry included Deputy National Security Adviser Benjamin Rhodes and senators John McCain, Harry Reid, Daniel Coats and Mary Landrieu.

Mr Obama speaks about the situation in Ukraine on the White House lawn

House of Representatives speaker John Boehner and the Head of the Senate Foreign Affairs Committee Robert Menendez are also barred, alongside Mr Obama's aides Caroline Atkinson and Daniel Pfeiffer.

The US is working with the European Union on a series of more stringent measures should the Kremlin continue in what Mr Obama described as an "illegitimate" incursion into the Crimean peninsula.

He said: "I signed a new executive order today that gives us the authority to impose sanctions not just on individuals but on key sectors of the Russian economy."

The US has declared Bank Rossiya, which serves a financial institution for senior Russian officials, and 20 individuals to be "Specially Designated Nationals".

This means the individuals' assets in the US will be frozen and they will be banned from entering the country.

Russia's Foreign Ministry said its retaliatory sanctions will "hit the United States like a boomerang".

"There should be no doubt: each hostile attack will be met in an adequate manner," the ministry said.

A spokesman for Mr Boehner said he was "proud" to be among those named, while Mr McCain has also reacted to Moscow's decision, saying: "I'm proud to be sanctioned by Putin - I'll never cease my efforts & dedication to freedom & independence of #Ukraine, which includes #Crimea."

Mr Obama has ruled out military action, but the G8 - a group of leading industrial nations, including Russia - has been suspended until the crisis is resolved.

Despite the sanctions, the Kremlin has cranked up its attempt to absorb Crimea into Russia.

Troops have seized military bases on the peninsula and on Thursday Russia's deputy defence minister Yuri Borisov said their military presence in Crimea would be bolstered to protect against "all possible encroachments" and to make it "a worthy representative of the Russian Federation".

This came as Russia's lower house of parliament overwhelmingly approved a treaty to annex Crimea from Ukraine.

There is now just one legal obstacle before Crimea is absorbed by Moscow - ratification from Russia's upper house - although little resistance is expected there.

Ukrainian troops in Crimea are currently being redeployed to the mainland by the Kiev government.

Ukrainian navy commander Serhiy Haiduk and several other hostages were detained by Crimean authorities on Wednesday but have now been released.